The National Park Service has successfully completed laser ablation tests to remove a biofilm that has darkened the surface of the Jefferson Monument’s dome. The effect of the biofilm, a colony of microscopic organisms, first became apparent in 2006 and has intensified since then. The laser ablation method was tested on 1000 of the dome’s 10,682 square feet. In this method, a finely tuned laser is used to remove the biofilm while leaving the underlying marble undamaged. The NPS hopes to clean the rest of the dome with this technology as part of a larger rehabilitation on the Washington, D.C. landmark in 2018.